Colin’s family continue to campaign for justice, recently taking a petition to the Scottish Parliament demanding an automatic FAI for all suspicious deaths. Bonar, who had a baby girl in September, signed the petition online.

Colin and Candice days before his death

But her friends and family were angered by posts on the Colin Marr Memorial Trust Facebook page, which keeps supporters updated on progress.

It has recently revealed that two detailed expert reports on the case, prepared by former head of CID at Yorkshire Police Tony Whittle, have been sent to the Crown Office.

It is understood these outline allegations that would amount to criminal activity by Fife Police and propose that some witnesses should be re-examined about their movements on the night Colin died.

Posts in response to recent updates have been hostile and aggressive, particularly in relation to Colin’s stepfather, Stuart Graham, described by one contributor as an “egotistical, fame-hungry a******e”.

Some comments accuse Colin’s family of “spreading poison” and wanting to destroy Bonar’s life. There was particular anger over a post that mentioned the death in custody of her uncle a month after Colin’s death.

Two of her aunts, Eve Malone and Dawn Wright, rang the Grahams’ doorbell last Saturday and demanded that no further mention be made of their brother.

Stuart said last night: “We could have debated it. We believe it was relevant to Fife’s lack of thoroughness in their investigation into Colin’s death.

“But they weren’t here for a debate. Dawn Wright repeated much of what was said online and personally attacked Margaret as a mother.

After more verbal nonsense, Margaret had to call the police and they removed them.”

Retired detective Whittle was introduced to the case in 2012 by Professor Mike Green, a pathologist consulted over Colin’s death.

Concerned by what he read when he reviewed case files, he agreed to help the family without charge.

He said: “This case reflects badly on some individuals and organisations. Colin’s family have had to battle for seven years to learn the truth about his death. There is still much to be done.”

Colin’s family learned recently that Cameron Ritchie, then area procurator fiscal for Fife, wrote to pathologist Derrick Pounder, also consulted over Colin’s death, in February 2008.

He expresses serious doubts a young man with no previous suicide attempts and no mental health problems would plunge a knife into his chest following a row with his girlfriend. He added that the force required “would have been very difficult to achieve”.